The sensitivity and specificity of the MTS tetrazolium assay for detecting the in vitro cytotoxicity of 20 chemicals using human cell lines

A number of studies reported that the MTS in vitro cytotoxicity assay is a convenient method for assessing cell viability. The main features found with this assay are its ease of use, accuracy and rapid indication of toxicity. It might well be a useful tool in human health risk assessment if it can be shown that this assay also has an acceptable sensitivity and specificity. This is of interest particularly when exposure to unknown chemical substances requires the rapid detection and evaluation of toxic effects. In this study, the cytotoxicity of 20 chemicals selected from the MEIC priority list was determined with the MTS assay. Since it could be shown that interactions between detection reagents and test chemicals might influence the results of this assay, preliminary experiments were carried out such that artifactual results due to test chemical interference could be excluded from this study. IC50 (50% inhibitory concentration) were established for each test chemical in two human cell lines (F1-73 and HeLa) and later compared with published toxicity data of the same chemicals established with in vitro and in vivo toxicological test systems. Direct comparisons of the data showed a generally lower sensitivity of the MTS assay, which is influenced by biological test organisms, cell type and exposure time. In terms of the specificity of the MTS assay, the results showed a good correlation between data obtained with the MTS assay and published data. The lowest correlation was found when the MTS assay was compared with in vivo studies, however, this finding corresponds well with other published in vitro-in vivo correlations. The highest correlation was found when the MTS assay was compared with test systems using human cell lines or exposure times of 3-24 h. Since the sensitivity of the MTS assay might be increased using different cell types or by extended incubation, this assay is found to provide ideal features of a good measurement system that might also be used for on site toxicological assessments.

Toxicity of Australian essential oil Backhousia citriodora (Lemon myrtle). Part 1. Antimicrobial activity and in vitro cytotoxicity

The antimicrobial and toxicological properties of the Australian essential oil, lemon myrtle, (Backhousia citriodora) were investigated. Lemon myrtle oil was shown to possess significant antimicrobial activity against the organisms Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, methicillin-resistant S. aureus (MRSA), Aspergillus niger, Klebsiella pneumoniae and Propionibacterium acnes comparable to its major component-citral. An in vitro toxicological study based on the MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) cytotoxicity assay was performed. In vitro cytotoxicity testing indicated that both lemon myrtle oil and citral had a very toxic effect against human cell lines: HepG2 (a hepatocarcinoma-derived cell line); F1-73 (a fibroblast cell line derived from normal skin) and primary cell cultures of human skin fibroblasts. Cytotoxicity IC50 (50% inhibitory concentration) values ranged from 0.008 to 0.014% (w/v) at 4 h to 0.003-0.012% (w/v) at 24 h of exposure. The no-observed-adverse-effect level (NOAEL) for lemon myrtle oil was calculated as 0.5 mg/l at 24 h exposure and the RfD (reference dose) was determined as 0.01 mg/l. A product containing 1% lemon myrtle oil was found to be low in toxicity and could potentially be used in the formulation of topical antimicrobial products.

Surface analysis of human plasma fibronectin adsorbed to commercially pure titanium materials

Protein binding on metallic implant surfaces, such as titanium, is governed by the physico-chemical nature of the metallic surface. Human plasma fibronectin (HPF) is an important matrix glycoprotein that mediates cell and protein attachment to each other or to the extracellular matrix present during wound healing. The objective of this study was to investigate the adsorption of HPF onto polished commercially pure titanium (cpTi) by using atomic force microscopy (AFM) and electron spectroscopy for chemical analysis (ESCA) and to measure the resultant surface contact angle before and after HPF binding. Two types of cpTi disks, one highly polished in our laboratory (HSS) and one commercially prepared (31), were reacted with HPF solutions of varying concentrations (1 microg/mL-10 ng/mL). ESCA survey spectra of samples coated with 1 microg/mL of fibronectin showed an increase in organic nitrogen and carbon compared with uncoated controls. Contact angle measurements of HSS and 31 cpTi disks showed no significant difference in average contact angle (36.3 degrees +/- 3.5 and 39.1 degrees +/- 3.1) despite differences in local root mean square (RMS) surface roughness (4.45 +/- 0.46 nm and 22.37 +/- 4.17 nm) as measured by AFM. Images obtained by AFM showed that 31 specimens were more irregular, with large parallel polishing grooves. Adsorbed HPF appeared in a globular form with an average length of 16.5 +/- 1.0 nm, a height of 2.5 +/- 0.5 nm, and a width of 9.6 +/- 1.2 nm. Fibronectin coating on both HSS and 31 cpTi specimens resulted in a significant increase in hydrophobicity compared to uncoated specimens. These results indicate the significance of HPF on cpTi and may explain how cpTi implants function in situ.

Adsorption and dissolution behavior of human plasma fibronectin on thermally and chemically modified titanium dioxide particles

Titanium is known for its biocompatibility and is widely used in dental and orthopedic reconstructive surgery. There are reports that osteointegration of these implants is not optimal. The objective of this study was to modify titanium dioxide particles and examine the resultant effects on protein adsorption to these altered surfaces using a model cell binding protein, human plasma fibronectin (HPF). HPF is an important matrix glycoprotein that plays a major role in cell and protein attachment, Titanium dioxide surfaces were modified by heating the titanium dioxide powder at 800 degrees C for 1 h or treating with an oxidizing agent: peroxide in ammonium hydroxide followed by peroxide in hydrochloric acid. Oxidized and control samples were further treated with 9:1 butanol:water for 30 min. Brunauer-Emmett-Teller showed no change in particle surface area as a result of thermal or chemical treatment. Hydrophobicity increased with butanol treatment of titanium dioxide. Diffuse reflectance Fourier transform infrared spectroscopy showed the presence of -CH2 and -CH3 vibrations in the region of 2850-3000 cm(-1) for both the heated, butanol and peroxide/butanol-treated samples. The absence of increased C-O and O-C=O features as determined by electron spectroscopy for chemical analysis indicates that butanol adsorption is not occurring via an esterification mechanism. The interaction between butanol and pre-heated or peroxide-treated titanium dioxide may be one of association (weak electrostatic and/or Van der Waals forces) rather than direct ionic bonding. Maximum HPF adsorption on modified or unmodified titanium dioxide occurred within 30 min, with greater protein adsorption occurring on butanol-treated samples. Desorption was minimal with all modifications. Zeta potential measurements showed that HPF adsorption caused an increase in the negative zeta potential with the greatest change noted for the butanol-treated samples. These findings suggest that wettability and surface charge both play an important role in protein adsorption to titanium dioxide. Thus, by modifying the physico-chemical properties of titanium dioxide surfaces, it may be possible to alter protein adsorption and hence optimize cell attachment.

Differentiation of human bone-derived cells grown on GRGDSP-peptide bound titanium surfaces

Various surface modifications have been applied to titanium alloy (Ti-6Al-4V) implants, in an attempt to enhance osseointegration; crucial for ideal prosthetic fixation. Despite the numerous studies demonstrating that peptide-modified surfaces influence in vitro cellular behavior, there is relatively little data reporting their effects on bone remodeling. The objective of this article was to examine the effects of chemically modifying Ti-6Al-4V surfaces with a common RGD sequence, a 15-residue peptide containing GRGDSP (glycine-arginine-glycine-aspartate-serine-proline), on the modulation of bone remodeling. The expression of proteins known to be associated with osseous matrix and bone resorption were studied during the growth of human bone-derived cells (HBDC) on these peptide-modified surfaces. HBDC grown for 7 days on RGD surfaces displayed significantly increased levels of osteocalcin, and pro-collagen Ialpha1 mRNAs, compared with the production by HBDC grown on the native Ti-6Al-4V. A pattern that was also reflected at the protein levels for osteocalcin, type I collagen, and bone sialoprotein. Moreover, HBDC grown for 7 and 14 days on RGD-modified Ti-6Al-4V expressed significantly higher level of osteoclast differentiation factors and lower levels of osteoprotegerin and IL-6 proteins compared with other surfaces tested. These results suggest that different chemical treatments of implant material (Ti-6Al-4V) surface result in differential bone responses, not only their ability to form bone but also to stimulate osteoclastic formation.

X-ray detectors at the Linac Coherent Light Source

Free-electron lasers (FELs) present new challenges for camera development compared with conventional light sources. At SLAC a variety of technologies are being used to match the demands of the Linac Coherent Light Source (LCLS) and to support a wide range of scientific applications. In this paper an overview of X-ray detector design requirements at FELs is presented and the various cameras in use at SLAC are described for the benefit of users planning experiments or analysts looking at data. Features and operation of the CSPAD camera, which is currently deployed at LCLS, are discussed, and the ePix family, a new generation of cameras under development at SLAC, is introduced.

Gestational exposure to loud noise alters the development and postnatal responsiveness of humoral and cellular components of the immune system in offspring

Gestational exposure of the female to environmental toxins can alter immune function in the offspring. We have recently shown that prenatal maternal stress, that is, stress applied to or induced in the female during pregnancy, can also alter the development of humoral immunocompetence in the offspring and their hormonal and immunologic responses to postnatal stress. This report presents data from two experiments on the effects of prenatal exposure to loud noise-prenatal sound stress (PSS)-on the development and responsiveness of in vitro and in vivo humoral and cellular immune function in the offspring. Pregnant rats were exposed daily from Day 15 to Day 21 of gestation to an inescapable loud noise (an 85- to 90-decibel fire alarm bell) delivered randomly for 1 hr. In developing offspring, PSS produced age-dependent and mitogen-specific alterations in lymphoproliferative activity and reduced immunoglobulin G levels at Postnatal Day 21. Antibody titers to herpes simplex virus type 1 were also reduced. Exposure to loud noise before or after infection produced an additional reduction in titers in these offspring. Arthus skin reaction (AR) to old tuberculin was reduced by PSS. Combined prenatal/postnatal sound stress further reduced this response and the AR to bovine serum albumin (BSA). Delayed hypersensitivity reaction to BSA was reduced in PSS offspring; postnatal sound stress enhanced the reaction to both antigens, but only in males. Antibody titers to BSA were increased by PSS; adjuvant-induced inflammation was attenuated by postnatal sound stress. These data suggest that in utero exposure to loud noise, which can occur in the workplace, is toxic to the developing immune system.

A novel technique for quantitative detection of mRNA expression in human bone derived cells cultured on biomaterials

A nonisotopic and quantitative in situ hybridization technique was adapted to investigate the effect of biomaterials on the cellular expression of mRNA from human bone derived cells (HBD cells). HBD cells were cultured for 24 or 48 h on tissue culture plastic, alumina, and ion modified alumina. Osteocalcin, osteopontin, alkaline phosphatase, type I collagen alpha 1, and type I collagen alpha 2 mRNAs were quantified. Protein expression for collagen types I, III, and V, and for anti-human macrophages CD68 (DAKO-CD68, KP1) and CD68 (PG-M1), and anti-human myeloid/histiocyte antigen (DAKO-MAC 387) were determined immunohistochemically using monoclonal antibodies. At 24 and 48 h, levels of mRNA for alkaline phosphatase and osteonectin were greater than mRNA levels for osteopontin, osteocalcin, collagen type I alpha 1, and collagen type I alpha 2 for cells grown on the three substrata. However, at 48 h mRNA levels for alkaline phosphatase and osteonectin were significantly higher on the modified ceramic substrata relative to the native alumina. HBD cells appear to express CD68-KP1 when cultured for 24 h. The techniques provide a sensitive and reproducible assay to evaluate gene and protein expression of cells grown on different substrata.

The functional expression of human bone-derived cells grown on rapidly resorbable calcium phosphate ceramics

The use of biodegradable bone substitutes is advantageous for alveolar ridge augmentation, since it avoids second-site surgery for autograft harvesting. This study examines the effect of novel, rapidly resorbable calcium phosphates on the expression of bone-related genes and proteins by human bone-derived cells (HBDC) and compares this behavior to that of tricalciumphosphate (TCP). Test materials were alpha-TCP, and four materials which were created from beta-Rhenanite and its derivatives: R1-beta-Rhenanite (CaNaPO(4)); R1/M2 composed of CaNaPO(4) and MgNaPO(4); R1+SiO(2) composed of CaNaPO(4) and 9% SiO(2) (wt%); and R17-Ca(2)KNa(PO(4))(2). HBDC were grown on the substrata for 3, 5, 7, 14 and 21 days, counted and probed for various mRNAs and proteins (Type I collagen, osteocalcin, osteopontin, osteonectin, alkaline phosphatase and bone sialoprotein). All substrata supported continuous cellular growth for 21 days. At day 21, surfaces of R1+SiO(2) and R17 had the highest number of HBDC. At 14 and 21 days, cells on R1 and on R1+SiO(2) displayed significantly enhanced expression of all osteogenic proteins. Since all novel calcium phosphates supported cellular proliferation together with expression of bone-related proteins at least as much as TCP, these ceramics can be regarded as potential bone substitutes. R1 and R1+SiO(2) had the most effect on osteoblastic differentiation, thus suggesting that these materials may possess a higher potency to enhance osteogenesis than TCP.

Effect of rapidly resorbable calcium phosphates and a calcium phosphate bone cement on the expression of bone-related genes and proteinsin vitro

The use of biodegradable bone substitutes is advantageous for alveolar ridge augmentation because it avoids second-site surgery for autograft harvesting. This study examines the effect of novel, rapidly resorbable calcium phosphates and a calcium phosphate bone cement on the expression of bone-related genes and proteins by human bone-derived cells (HBDCs) and compares this behavior to that of tricalciumphosphate (TCP). Test materials were alpha-TCP, two materials with a crystalline phase Ca(2)KNa(PO(4))(2) and with a small amorphous portion containing either magnesium potassium phosphate (material denominated GB14) or silica phosphate (material denominated GB9), and a calcium phosphate bone cement (material denominated Biocement D). HBDCs were grown on the substrata for 3, 7, 14, and 21 days, counted, and probed for various mRNAs and proteins (type I collagen, osteocalcin, osteopontin, osteonectin, alkaline phosphatase, and bone sialoprotein). All substrates supported continuous cellular growth for 21 days. In the presence of GB14 and Biocement D specimens cell proliferation was reduced and cell differentiation increased. At day 21, the greatest number of cells was found on GB9 expressing significantly higher levels of bone-related proteins than cells grown on all other surfaces. Because all novel materials facilitated the expression of the osteoblastic phenotype at least as much as TCP and the polystyrene control, these biomaterials can be regarded as excellent candidate bone substitute materials. GB9 induced the highest proliferation and cellular differentiation after 21 days of incubation, suggesting that this material may possess a higher potency for enhancing osteogenesis than TCP.

In vitro cytotoxicity of selected chemicals commonly produced during fire combustion using human cell lines

Fire combustion products contain a broad range of chemicals, which have a multitude of possible toxic interactions in humans. The aim of this study was to evaluate the cytotoxicity of selected substances commonly produced during fire combustion. A range of human cell lines and cultures including: skin fibroblasts, HepG2 (liver derived), and A549 (lung derived cells) were used to represent different human target organs. The colorimetric MTS assay (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) was used to detect the cytotoxic effects of selected substances including: acetic acid, ammonia, formaldehyde, hydrobromic acid, hydrochloric acid, hydrofluoric acid, potassium cyanide, sodium fluoride, sodium nitrite, sodium sulphide, and sulphurous acid. In this study, the NOAEC (No Observable Adverse Effect Concentration), IC(10) (10% inhibitory concentration), IC50 (50% inhibitory concentration), and TLC (Total Lethal Concentration) values were determined. The ratio between in vitro IC50 to in vivo human toxicity data (Lowest Lethal Dose-LDLo and Lowest Lethal Concentration--LCLo) was also established. Results indicated a strong relationship between IC50 values on the cell types used: fibroblast and A549 (R2: 0.92), A549 and HepG2 (R2: 0.72), fibroblast and HepG2 (R2: 0.69). Good correlation was obtained between the IC50 against LDLo and LCLo when an appropriate adjustment factor was implemented. Results of this study indicated that in vitro methods could be a potential technique for assessing the toxicity of fire combustion products.

Toxicity of Australian essential oil Backhousia citriodora (lemon myrtle). Part 2. Absorption and histopathology following application to human skin

The in vitro percutaneous absorption of the essential oil of lemon myrtle (Backhousia citriodora) has been studied in freshly excised human full-thickness abdominal skin obtained from patients undergoing elective surgery. Absorption of lemon myrtle oil in human skin discs (4.9 cm(2)) was evaluated using a Franz cell diffusion system following topical application of neat lemon myrtle oil (100 microl or 18.29 mg/cm(2)) to the epidermal surface at exposure durations of 1 to 12 h. Gas chromatography mass spectrometry (GCMS) was used as an analytical technique to determine the absorption of lemon myrtle oil components in full-thickness skin. Citral; (consisting of isomers, geranial and neral) was the only component of lemon myrtle oil found to be absorbing into skin at all exposure periods. At the maximum exposure duration of 12 h, the total absorption of citral in the full-thickness skin disc was 0.29+/-0.07 mg/cm(2) (mean+/-S.D., n=4) of the applied dose. Although the absorption of lemon myrtle oil components was limited, haematoxylin and eosin (H&E) staining showed significant losses in the cellular functioning of skin including; losses of integrity and solubilisation of the stratum corneum, cellular necrosis (to 15%) and cellular vacuolation (to 25%) on comparison to control skin. When a formulated product containing 1% lemon myrtle oil (0.18 mg/cm(2)) was applied to human skin discs (4.9 cm(2)) at 8 h exposure the total absorption of citral in the full-thickness skin disc was 5.12+/-0.60 x 10(-4) mg/cm(2) (mean+/-S.D., n=4) of the applied dose. No other components were detected. The histopathological assessment indicated limited damage to epidermal cells. The combination of the above methodologies enabled the generation of data that could be used for a comprehensive evaluation of the toxicity effects of lemon myrtle oil for topical application.

Prosthetic particles modify the expression of bone-related proteins by human osteoblastic cells in vitro

Loss of bone near joint prostheses is thought to be caused by activation of recruited osteoclasts by osteolytic mediators induced by wear particles. It is proposed that particles inhibit osteogenesis during bone remodelling causing a reduction in the levels of peri-implant bone. This study explores whether prosthetic particles modulate bone formation by affecting osteoblastic bone-related mRNAs (alkaline phosphatase, pro-collagen Ialpha1, osteopontin, osteonectin, osteocalcin, bone sialoprotein and thrombospondin) or their translated proteins using titanium alloy, commercially pure titanium, and cobalt-chrome particles. The direct effect of the particles revealed no change to the expression of the bone-related mRNAs in human bone-derived cells (HBDC) at the time points investigated; although non-collagenous translated proteins expressed by these HBDC were significantly effected (p<0.05). Different patterns of expression for bone-related proteins were induced by the different particles both directly and indirectly. Inflammatory mediators (interleukin-1beta, tumor necrosis factor alpha, interleukin-6, and prostaglandin E2) had similar effects on HBDC to the media obtained from monocytes incubated with particles. This study shows that prosthetic wear particles can significantly modify the expression of bone-related proteins by osteogenic cells in vitro. These alterations in osteogenic activity at the interface of the implant and bone may be an important factor in the failure of many orthopaedic implants.

Microstructure and biopharmaceutical performances of curcumin-loaded low-energy nanoemulsions containing eucalyptol and pinene: Terpenes' role overcome penetration enhancement effect?

The objective of this work was to develop low-energy nanoemulsions for enhanced dermal delivery of curcumin, using monoterpene compounds eucalyptol (EUC) and pinene (PIN) as chemical penetration enhancers. Spontaneous emulsification was the preparation method. All formulations contained 10% of the oil phase (medium-chain triglycerides (MCT), or their mixture with EUC or PIN). Formulations were stabilized by the combination of polysorbate 80 and soybean lecithin (surfactant-to-oil-ratio=1). Concentration of curcumin was set to 3 mg/ml. Average droplet diameter of all tested formulations ranged from 102 nm to 132 nm, but the ones containing monoterpenes had significantly smaller size compared to the MCT formulation. Such finding was profoundly studied through electron paramagnetic resonance spectroscopy, which proved that the presence of monoterpenes modified the nanoemulsions' interfacial environment, resulting in droplet size reduction. The release study of curcumin (using Franz cells) demonstrated that the cumulative amount released after 6 h of the experiment was 10.1 ± 0.2% for the MCT nanoemulsions, 13.9 ± 0.1% and 14.0 ± 0.2% for PIN and EUC formulations, respectively. In vivo tape stripping revealed their performances in delivering curcumin into the skin, indicating the following order: EUC>MCT>PIN. The formulation with EUC was clearly the most successful, giving the highest cumulative amount of curcumin that penetrated per surface unit: 34.24±5.68 µg/cm². The MCT formulation followed (30.62±2.61 µg/cm²) and, finally, the one with PIN (21.61±0.11 µg/cm²). These results corelated with curcumin's solubility in the chosen oils: 4.18±0.02 mg/ml for EUC, 1.67±0.04 mg/ml for MCT and 0.21±0.01 mg/ml for PIN. Probably, higher solubility in the oil phase of the nanoemulsion promoted curcumin's solubility in the superficial skin layers, providing enhanced penetration.

Quantitation of Fc gamma RII mRNA in platelets and megakaryoblastic cell lines by a new method of in situ hybridization

We have developed a highly sensitive and quantitative, non-isotopic method of in situ hybridization in which the level of probe binding to intracellular mRNA is determined using an ELISA based detection method. Highly purified cell preparations or cells from a cultured cell line are centrifuged into 96 well microtiter plates. The cells are fixed with formalin and pre-treated with Triton X-100 and Nonidet P40 before photobiotin labeled cDNA probes are applied. The biotin from the hybridization is detected using multiple applications of streptavidin and biotinylated alkaline phosphatase and then visualized by the p-NPP (p-nitrophenyl phosphate) conversion method. We have determined a number of the optimal parameters in the procedure including the effects of cell numbers per well, development times and standardization of data using ubiquitous beta-actin mRNA and poly-A+ RNA expression as controls. We have used the technique to study the level of expression of FcgR mRNA in platelets and precursors. We found that platelets and megakaryoblastic cell lines only express mRNA for Fc gamma RII. The presence of the Fc gamma RII molecules was confirmed by complementary studies using immunohistochemistry with specific monoclonal antibodies IV.3 and KB61.

Quantitation of soluble and membrane-bound Fc gamma RIIA (CD32A) mRNA in platelets and megakaryoblastic cell line (Meg-01)

Fc gamma receptors (Fc gamma Rs) are glycoproteins on platelet surface that bind IgG-containing immune complexes. However, excessive binding of immune complexes leads to platelet activation and thrombosis or increased platelet clearance and thrombocytopenia. In this study, Fc gamma R transcripts in platelets and megakaryoblastic cell line (Meg-01) were investigated using specifically designed oligonucleotides and a new quantitative in situ hybridization assay. Platelets and Meg-01 cells were found to express only Fc gamma RII transcripts. Of Fc gamma RIIA mRNA isoforms (Fc gamma RIIA, B and C), Fc gamma RIIA mRNA predominates in these cells. Platelets and Meg-01 cells contain both alternative spliced forms of Fc gamma RIIA mRNA, those with and without the transmembrane (TM) exon and both forms were present in near equal amounts. In contrast, Fc gamma RIIA transcript with the TM exon predominates in neutrophils and monocytes, suggesting that the splicing of the TM exon is under lineage-specific control.

In vitro cytotoxicity testing of airborne formaldehyde collected in serum-free culture media

The purpose of this study was to identify a suitable sampling model for on-site toxicity assessment of soluble air contaminants such as formaldehyde, a well known industrial and indoor air contaminant. The in vitro cytotoxicity of formaldehyde, the selected model for soluble air contaminants, was studied using the MTS (tetrazolium salt) assay in two carcinoma cell lines, A549 epithelial lung and HepG2 hepatocarcinoma, and in skin fibroblasts. The cytotoxic effects of airborne formaldehyde were evaluated using test atmospheres in concentrations below 10 ppm (12.3 mg/m3), generated by a dynamic diffusion method and bubbled (0.3 L/min) through serum-free culture media for one or four hours. Human cells were treated with formaldehyde air samples, and cell viability was determined after four hours incubation. In parallel, the concentration of airborne formaldehyde was monitored, using the 3500 NIOSH method. Cell viability of the HepG2 cells exposed to formaldehyde air samples (8.75 ppm-4 h) was reduced to less than 50% (31.69/1.24%). The HepG2 cell lines were found to be more sensitive (IC50=103.799/23.55 mg/L) to formaldehyde than both A549 cell lines (IC50=198.369/9.54 mg/L) and skin fibroblasts (IC50=196.689/36.73 mg/L) (PB/0.01). An average of 96.8% was determined for collection efficiency of formaldehyde in serum-free culture media. The results of this study suggest that absorption of soluble air contaminants, such as formaldehyde, in serum-free culture media can be used as a suitable sampling model for on-site toxicity assessments.

A sensitive method for the detection of poly-A tails of mRNA using a biotin-labelled heteropolymer OF dT:rA

We have developed a highly sensitive non-radioactive in situ hybridization technique that enables us to study the production of mRNAs in tissues. As part of the validation procedure of our methods, we examined various methods of detecting poly-A RNA tails of mRNA. We have used three types of biotin-labelled probes complementary to poly-A sequences: a 25-mer poly-dT oligonucleotide, a polymer of dT, and a heteropolymer of dT:rA. All the probes had the same specificity of reactivity but the heteropolymer of dT:rA gave the strongest signals as visualized histochemically by the use of alkaline phosphatase as the detection enzyme. All the probes tested for poly-A detection showed reactivity. The poly-dT oligonucleotide showed a strength of signal comparable to published results. The biotinylated polymer of dT gave a stronger signal than that of the oligonucleotide, and the heteropolymer was the strongest of all. The strong signal seen with the heteropolymer probe is due to probe complexing during hybridization, in which additional binding between sense and antisense strands of the probe (i.e. poly-rA and poly-dT) amplifies the number of biotin molecules at the hybridization site; this strategy has been exploited by us as a means of visualizing low copy numbers of specific mRNAs.

Macrophages at the skeletal tissue-device interface of loosened prosthetic devices express bone-related genes and their products

Aseptic loosening of prosthetic arthroplasty is the most common reason for implant failure in adult orthopaedic reconstruction. At the interface of aseptic loosened prostheses, there is an abundance of particle-activated macrophages and other inflammatory cells. The role of these particle-laden macrophages in the osteogenic arm of the remodeling skeleton in this pathological condition is poorly understood. Molecular signaling by mesenchymal cells and mononuclear inflammatory cells residing in the interfacial tissues between bone and cement or prosthetic material of aseptically loosened joint prostheses was studied using in situ hybridization and immunohistochemical techniques. We found that a range of collagenous and noncollagenous matrix proteins, including osteopontin, osteocalcin, bone sialoprotein, and type I collagen, were produced in the periprosthetic tissue by foamy macrophages, as well as nearby osteogenic cells. The former accumulated in profusion in the three zones of interfacial tissues: pseudomembranous, fibrous, and osseous. Spindle mesenchymal cells in the fibrous zone failed to express any of the osteogenic mRNAs or proteins sought. The expression of bone-related genes and proteins by foamy macrophages at the interface of an aseptic loosened prosthesis may contribute to the disturbance of bone remodeling at this site.

The Role of Oxidative Stress in the Clinical Manifestations of Childhood Asthma

INTRODUCTION

The significance of oxidative stress in pathogenesis of childhood asthma was recognized, but its role in the clinical manifestations of disease is still unclear.

MATERIALS AND METHODS

The study was conducted in 96 asthmatic children. The urinary biomarker of oxidative stress, 8-oxo-7,8-dihydro-2-deoxyguanosine (8-oxodG/creatinine) was determined by using HPLC-MS/MS. ELISA was performed to measure myeloperoxidase (MPO) and Cu,Zn- superoxide dismutase (Cu,Zn-SOD) in serum.

RESULTS

Logistic regression analysis revealed that female gender, tobacco smoke exposure, and increased 8-oxodG/creatinine were associated with risk for intermittent asthma, while the positive allergy test and increased Cu,Zn-SOD were associated with eczema in asthmatic children. Higher MPO (p = 0.033), and percent of granulocytes (p = 0.030) were found in severe persistent asthma in comparison to intermittent or mild persistent asthma.

CONCLUSION

The main findings that TSE-induced oxidative stress is a risk for intermittent asthma and eczema may be clinically significant for the disease prevention and therapeutic improvements.

Human cell line toxicity of binary and ternary chemical mixtures in comparison to individual toxic effects of their components

Contaminated site projects involve health risk assessment procedures that must consider potential interactive effects of present contaminants. In order to establish a quick and reliable method that accounts for smaller than additive, additive, or greater than additive toxic effects, this study compared the cytotoxicity of 34 binary and ternary chemical mixtures of four structurally different chemicals to HeLa cells. Further, five blind samples of these mixtures or their components were tested to determine the ability to identify unknown mixtures. The colorimetric MTS in vitro cytotoxicity assay was used to detect cytotoxic effects after the cells were exposed for 1 h to serial dilutions of the mixtures. Experimental cytotoxicity data were compared and set against data predicted by a mathematical algorithm. They mainly showed additive effects of the components in mixture but also identified smaller than additive and greater than additive effects. A subjective classification scheme allowed evaluation of the toxicity of the blind samples in comparison to results from the study on binary and ternary mixtures tested before. This scheme focused on quantitative cytotoxicity data as well as on the slope of the concentration-effect curves and demonstrated the use of the MTS assay for human health risk assessments in the context of contaminated sites.

Quantitative aspects of an in situ hybridization procedure for detecting mRNAs in cells using 96-well microplates

The universal quantitation of the DNA hybridization reaction has been a goal sought by many researchers. Part of this search has been the need to develop a rapid, sensitive, easy-to-perform, and quantitative method to measure the abundance of specific mRNAs directly within cells. Conventionally mRNA detection can be done by advanced quantitative in situ hybridization (ISH) using either image analysis or fluorescence in situ hybridization (FISH), or indirectly by extraction of mRNA from cells or tissue and using Northern blot or quantitative polymerase chain reaction (PCR). We examined the quantitative nature of probe binding to intracellular mRNA in a sensitive and easy-to-use nonisotopic method of ISH previously developed in our laboratories. The method is applicable to isolated primary cells or cells in culture. The procedural details are very simple, with cells being centrifuged into 96-well microplates, fixed with formalin, and pretreated with Triton X-100 and Nonidet P-40 before photobiotin-labeled cDNA probes are applied. Biotin from the hybridization of probe to target is detected using multiple applications of streptavidin and biotinylated alkaline phosphatase and visualized by the p-nitrophenyl phosphate conversion method. The quantitative parameters of the ISH procedure were determined by measuring the levels of expression of erythropoietin (EPO) mRNA and its translated protein in transfected COS-7 cells. There is a log-linear relationship between the levels of signal obtained in the ISH reaction in 96-well microplates and the EPO protein levels measured by enzyme-linked immunosorbent assay (ELISA). This demonstrated relationship is important in the standardization and use of these procedures to measure quantitatively mRNAs within cells.

Oxidative Stress and Genetic Variants of Xenobiotic-Metabolising Enzymes Associated with COPD Development and Severity in Serbian Adults

The genetic and non-genetic factors that contribute to the development of chronic obstructive pulmonary disease (COPD) are still poorly understood. We investigated the potential role of genetic variants of xenobiotic-metabolising enzymes (glutathione-S-transferase M1, GSTM1; glutathione-S-transferase T1, GSTT1; microsomal epoxide hydrolase, mEH), oxidative stress (assessed by urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine, 8-oxodG/creatinine), sex, ageing and smoking habits on susceptibility to development of COPD and its severity in Serbian population. The investigated population consisted of 153 healthy subjects (85 males and 68 females) and 71 patients with COPD (33 males and 38 females). Detection of GSTM1*null, GSTT1*null, mEH Tyr113His and mEH His139Arg gene variants was performed by PCR/RFLP method. Urinary 8-oxodG was determined using HPLC-MS/MS, and expressed as 8-oxodG/creatinine. We revealed that increased urinary 8-oxodG/creatinine and leucocytosis are the strongest independent predictors for COPD development. Increased level of oxidative stress increased the risk for COPD in males [odds ratio (OR), 95% confidence interval (CI): 8.42, 2.26-31.28], more than in females (OR, 95% CI: 3.60, 1.37-9.45). Additionally, independent predictors for COPD were ageing in males (OR, 95% CI: 1.29, 1.12-1.48), while in females they were at least one GSTM1 or GSTT1 gene deletion in combination (OR, 95% CI: 23.67, 2.62-213.46), and increased cumulative cigarette consumption (OR, 95% CI: 1.09, 1.01-1.16). Severity of COPD was associated with the combined effect of low mEH activity phenotype, high level of oxidative stress and heavy smoking. In conclusion, early identification of GSTM1*null or GSTT1*null genotypes in females, low mEH activity phenotype in heavy smokers and monitoring of oxidative stress level can be useful diagnostic and prognostic biomarkers.